ISS Astronauts Have a Spacewalking Close Call

Astronauts had to return to the ISS just one and a half hours into a spacewalk today after water began leaking into the helmet of European Space Agency astronaut Luca Parmitano. PopMech contributor and former astronaut Tom Jones reports.

Astronauts train for their spacewalks at the International Space Station while submerged in Houston in a six-million-gallon water tank, learning to better understand and cope with the free-fall environment of orbital flight. But they expect to leave all that water behind after launch.

Today at the ISS, however, an unusual and serious water leak threatened to engulf European Space Agency astronaut Luca Parmitano, nearly blinding him inside his helmet and forcing NASA to cut short their maintenance spacewalk after just 1 hour and 32 minutes. Parmitano made it back inside the station safely, and Tuesday afternoon NASA officials told the media they were still investigating how this water leak could have happened.

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About an hour into the EVA (extravehicular activity), Parmitano first reported water building up inside his helmet, spreading on the back of his head. "I don't understand where it's coming from," Parmitano said. Initially, both he and partner Chris Cassidy suspected the source was a 32-oz. drink bag, which rides inside the front torso of the spacesuit, its drinking valve positioned for sipping just above the suit's neck ring. But Parmitano, an Italian air force pilot and engineer, reported that he felt the water slowly expanding, threatening to envelop his head and face in a clinging, choking blanket of H2O. "I can still hear perfectly, but my head is really wet and I feel it increasing," Parmitano said.

In the free-fall of Earth orbit, water's surface tension, (the cohesive force that draws water molecules together) causes it to coalesce into a drifting blob. Once a globule strikes a surface, it clings to it and spreads, forming an enveloping film. I encountered this same phenomenon when working out vigorously on the shuttle's bicycle ergometer: Perspiration clung to my neck and face, spreading into and stinging my eyes.

Of course, I had a towel ready to deal with too much sweat. Inside his sealed helmet, Parmitano could not wipe the water from his face. Shaking his head might throw some of the clinging water off his face, but it might then adhere to the inside of the helmet visor, cutting off his vision. And drifting water could pose a choking hazard should Parmitano inhale droplets into his lungs.

As the seconds went on, the accumulating water kept spreading toward Parmitano's face. "Now it's in my eyes," he reported. Ground controllers reacted quickly, ordering the pair to end the spacewalk and return to the airlock.

In just the few minutes it took for the Italian astronaut to reach the Quest airlock, water had seeped into his communications headphones and microphone. Unable to talk to Parmitano by radio during their repressurization from vacuum, Cassidy directed, "Squeeze my hand if you're fine." Radioing Mission Control, Cassidy added, "He looks fine. He looks miserable, but he's okay."

Using an expedited suit-doffing procedure that skipped some routine steps to save time, the pair's ISS crewmates quickly equalized the air pressure between Quest and the station interior. Within ten minutes, they had Parmitano out of his helmet, toweling him dry. In the hours after the spacewalk, both crewmembers reported no ill effects.

Late on Tuesday, NASA flight controllers continued their search for the source of the water leak. The drink bag, the initial suspect during the EVA, doesn't hold enough water to have doused Parmitano so thoroughly. But the suit's water supply system, which circulates chilled water through an astronaut's "long underwear" cooling garment and feeds a sublimator heat exchanger, contains about a gallon. That's more than enough to have caused the flood in Parmitano's helmet, estimated at about 1 to 1.5 liters.

ISS mission management team leader Kenneth Todd, joined by flight director David Korth and EVA officer Karina Eversley, confirmed the seriousness of the problem at an afternoon press conference. Korth noted that EVAs are already dangerous. For Parmitano, this experience was like plunging one's head into a sloshing fishbowl, with no way to get it off.

Eversley agreed that the choking hazard from inhaled water was real, and it eventually caused flight controllers to terminate the spacewalk. Todd said he was proud of the way the ISS team handled the near-emergency, one they had never encountered before. "The crew was cool and expert in reporting and diagnosing the problem. Our training on the ground paid off, and the team kept its eye on the main objective"—the crew's safety.

Planetary scientist and veteran astronaut Tom Jones recounted his three spacewalks at the International Space Station in Sky Walking: An Astronaut's Memoir.